This invention is directed to telephone systems and, more particularly, to telephone signal processing systems, such as tone-to-pulse converters, for example.
In many telephone systems, it is necessary to perform signal processing for one reason or another. One of the most common forms of signal processing presently in use is the conversion of DTMF signals generated by touch tone telephones into rotary dial-type pulses suitable for use by "downstream" switching systems. Such conversion is often necessary because many downstream switching systems are not operable by DTMF signals directly. The telephone signal processor, or in this case, tone-to-pulse converter, may be allotted to a plurality of telephone lines. In such a case, the circuit providing access to the telephone lines is usually referred to as a port. Each port includes an array of electronic circuitry adapted to route signals, in this case DTMF signals, from associated linefinders to the tone-to-pulse converter, and from the tone-to-pulse converter to associated first selectors. The port may, in this context, be either dedicated to a specific signal converter, or be constructed to operate in conjunction with a pool of converters via some type of allotter switch.
In the past, the ports have been dedicated to associated linefinders and first selectors on a one-to-one basis. However, this arrangement has been more expensive than desirable because in many instances port use is only required for a small portion of the time that a particular telephone line is seized. For example, if tone-to-pulse signal processing is required, port usage only occurs during the dialing interval, not during the conversation interval of a total line seizure interval. Thus, in the past, ports have been idle for extended periods of time. Obviously, idle equipment is not cost effective, i.e., it is not cost effective on a cost-per-use basis. In the case of ports, idleness is particularly undesirable because ports are relatively expensive electronic circuits.
Therefore it is an object of this invention to provide an apparatus for reducing the number of ports needed in a telephone signal processing system, such as a tone-to-pulse conversion system.
It is a further object of this invention to provide a port multiplexer suitable for utilizing ports in a more efficient manner.
It is a still further object of this invention to provide an apparatus for use in a telephone signal processing system that reduces the idle time of the ports forming a portion of such a system.